What are some off-the-beaten-path things to do in the Florida Keys?

Mike and I are staying at his ‘rents’ beach house down there in a week, and as we went last year and did most of the tourist-y stuff then, we are hoping to find some lesser-known treasures on this visit. Do any of y’all have any suggestions?

By the way, we aren’t big on drinking or eating out.

Thanks in advance!